21.—(1) A relevant highway authority and the undertaker may enter into agreements with respect to—
(a)the construction of any new highway, including any structure carrying the highway over or under a railway authorised by this Order;
(b)the strengthening, improvement, repair or reconstruction of any highway under the powers conferred by this Order;
(c)the maintenance of the structure of any bridge carrying a highway over or under a railway;
(d)the maintenance of landscaping within a highway constructed as part of the highway works;
(e)any stopping up, alteration or diversion of a highway as part of or to facilitate the authorised development; or
(f)the carrying out in the highway of any of the works referred to in article 10 (highway works).
(2) Such an agreement may, without limitation on the scope of paragraph (1)—
(a)make provision for the relevant highway authority to carry out any function under this Order which relates to the highway in question;
(b)include an agreement between the undertaker and relevant highway authority specifying a reasonable time for the completion of the works; and
(c)contain such terms as to payment and otherwise as the parties consider appropriate.